I'd shoot it the way it is. What you're looking to do is going to end up costing another $150 dollars before the price of the scope.
If you don't want to damage the rifle (but who are we kidding, this isn't a K98 with german markings unpeened) and can stand the look, you can get an S&K insta-mount that attaches to the rear sight. You'll have to use a pistol scope though.
A Mojo peep sight is another option but it's both gimmicky (peep is so far forward on the gun) and it's pretty expensive.
Overall, if you want a scoped rifle the Stevens, Marlin, Howa, Mossy, etc is always going to be the best value and return for your money.
If you spent 100 for the gun plus 150 put into into and decide to sell the gun, you'll get about 100 dollars.
I'd keep the Mosin as is.